When user equipment (UE) is powered on and is attached to a network, an evolved NodeB (eNB) selects a proper mobility management entity (MME) that serves the UE, and then the MME selects a proper serving gateway (S-GW) and a proper packet data network gateway (P-GW) that serve the UE. A data packet transmitted by the UE is transmitted over an evolved packet system (EPS) bearer between the UE and the P-GW, and each EPS bearer includes three parts: a radio bearer between UE and a base station, an S1 bearer between the base station and an S-GW, and an S5/S8 bearer between the S-GW and a P-GW.
Functions executed by the P-GW on the data packet mainly include lawful interception, charging, filtering a data packet of an external PDN network, and the like. When two UEs perform communication by using a same P-GW and the foregoing actions do not need to be performed (for example, lawful interception and monthly charging of a user are not performed), a manner of optimizing a route between S-GWs may be used, so that data does not pass through the P-GW. When S-GWs of two networks communicate directly, a routing loss is reduced. When two UEs are served by a same S-GW, and a base station 1 receives user data, the base station 1 routes the user data to the S-GW according to a method in the prior art, and the S-GW sends the user data to a base station 2, where the S-GW executes only a forwarding function, which causes non-optimum routing and causes a delay.